Wireless sensing system

ABSTRACT

A wireless sensing system and method for wireless sensor interrogation are disclosed. The wireless sensing system includes a plurality of radio frequency sensors distributed within a predefined area, a forward communication link with an energizer coupled to a transmission cable. The energizer is adapted to provide radio frequency signals intended for the plurality of radio frequency sensors to the transmission cable. The transmission cable is adapted as a leaky waveguide antenna selectively slotted and routed within the predefined area for effective air linking of leaked radio frequency signals to the plurality of wireless sensors. The method for wireless sensor interrogation includes providing a plurality of radio frequency sensors distributed within a predefined area, providing a forward communication link including an energizer coupled to a transmission cable, routing the transmission cable through the predefined area in proximity to the plurality of radio frequency sensors, selectively slotting the transmission cable in regions proximate the plurality of radio frequency sensors, transmitting radio frequency signals through the transmission cable, and air linking radio frequency signals to the plurality of radio frequency sensors through the slotted regions proximate the plurality of sensors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Ser.No. 60/713,924 filed Sep. 2, 2005.

TECHNICAL FIELD

The present invention is related to sensors and switches. Moreparticularly, the invention is concerned with wireless sensors andswitches.

BACKGROUND OF THE INVENTION

Devices and systems are known for enabling secure, keyless accesscontrol including vehicular access control. An authorized personpossesses a radio frequency (RF) device, for example an RFidentification (ID) tag embedded in an identification badge or creditcard-type medium to enable access. Building access systems may rely uponswiping the badge or card through an energizer/reader which interrogatesthe RFID tag and verifies that certain information carried by the RFIDtag meets the security requirements to allow access. Similarly, avehicular access control system may rely upon door handle activation toinitiate an interrogation and verification. If the door handle operatorpossesses a key, a key fob, badge, card or the like including an RFIDtag with information meeting the security requirements, the door locksare actuated to provide access to the vehicle. Additional interrogationmay enable operative functionality of the vehicle systems, includingkeyless push-button starting, in similar fashion. Related RF basedsystems are in use for authorizing purchases where small RF devicesintended primarily for coupling to a key chain are brought intoproximity of an RF energizer/reader associated with a dispensingmechanism for the product being purchased. In such systems, the RFdevice stores information related to the user's credit card account forcompleting the transaction. Other systems are known for automating thecollection process on toll roads where an RF device carried by a vehicleis interrogated and communicates information back to an RFenergizer/reader associated with certain designated toll collectionbooths.

Passive wireless devices (i.e. those requiring interrogation beforetransmission) may be categorized as backscatter type which reflects backa characteristic signal to the energizer/reader subsequent to theenergizer/reader sending an interrogation signal. The energizer/readercan identify and distinguish unique backscatter signatures. This type ofwireless system is generally a lowest cost approach. Another type ofwireless system receives the interrogation signal, rectifies the RFenergy to a DC source and uses the DC energy to send information storedin sensor memory. Another type has its own power source—commonly abattery. The battery may be completely independent of the RFenergizer/reader energy or alternatively recharged by the RFenergizer/reader signal. In both of these latter wireless systems, theRF signal serves to interrogate or wake up the wireless device. Suchwireless devices use the interrogation signal for initiating theprovision of stored information back to the energizer/reader.

Electromagnetic emissions are regulated. Such regulations limit the RFenergy emitted by an energizer/reader in the frequency band where RFdevices operate. Current United States regulations limit such energyemissions to 4 watts. Similar regulations exist in other countriesaround the world. Such energy restrictions effectively limit theeffective range between the energizer/reader and the RF device.

The communication links of an RF system including an energizer/readerand remote RF device are not balanced. That is to say, theenergizer/reader emits a relatively greater amount of RF energy thandoes the RF device. The energizer/reader must be located close enough tothe RF device to effectively energize and/or interrogate the RF deviceto effect the desired return response from the device. If too far awayfrom the energizer/reader, or in an area of attenuated RF signal, the RFresponsive device will not receive enough energy to backscatter, toappropriately energize and effect a response, or to distinguish theenergizer/reader emission as an interrogation looking for a response.

RF device communication systems are generally limited due toregulations. Beginning with the forward communication link powerlimitation, losses in communicating to the RF device include propagationlosses, RF device antenna inefficiencies and losses in the energy andsignal conversions for signal processing and energy utilization at theRF device. And, these same types of inefficiencies are repeated withinthe RF device in the reverse communication link from the RF device tothe energizer/reader. The remaining reverse communication link, whichincludes the energizer/reader front end and digital signal processing,however, is more robust being characterized by effective noise immunityand the ability to detect relatively low level signals. Therefore, RFdevice communication systems are generally more limited with respect tothe forward communication link than with respect to the reversecommunication link.

Effective systems therefore require designed proximity and orientationbetween the energizer/reader and the RF device to ensure properoperation. In conventional applications, the energizer/reader and the RFdevice are dynamically manipulated such that the proximity andorientation requirements for effecting the desired interaction are met.This may include, for example, manipulating the RF device into anappropriate position relative to a static energizer/reader, manipulatingthe energizer/reader into an appropriate position relative to a staticRF device or combinationally manipulating the RF device and theenergizer/reader into an appropriate cooperative orientation. Suchsystems are used, for example, in inventory management control andproduct tracking. One such system may convey goods carrying an RF devicealong a defined path which includes an energizer reader oriented suchthat the conveyance brings the RF device within the proper proximity andorientation of the energizer/reader to effect the desired operation.Another such system may make use of a portable or maneuverableenergizer/reader for spot checking material at various ad-hoc locationswithin a distribution chain—for example at a receiving dock, a warehouseor just about anywhere within a distribution chain—by maneuvering theenergizer/reader within the proper proximity and orientation of the RFdevice to effect the desired operation. These systems tend to becharacterized by relatively narrow interrogation fields relative to theenergizer/reader within which the RF device can be made to, or isreasonably anticipated to, temporally but sufficiently reside to effectthe desired interrogation. These systems are not generally concernedwith wide range interrogation fields which, in fact, might undesirablyinitiate unintentional interrogations of RF devices away from theintended RF device thereby complicating energizer/reader tasksassociated with intelligibly discerning return signals.

SUMMARY OF THE INVENTION

A wireless sensing system includes a plurality of radio frequencysensors distributed within a predefined area. The wireless sensingsystem further includes a forward communication link with an energizercoupled to a transmission cable. The energizer is adapted to provideradio frequency signals intended for the plurality of radio frequencysensors to the transmission cable. The transmission cable is adapted asa leaky waveguide antenna selectively slotted and routed within thepredefined area for effective air linking of leaked radio frequencysignals to the plurality of wireless sensors.

A method for wireless sensor interrogation includes providing aplurality of radio frequency sensors distributed within a predefinedarea. The method for wireless sensor interrogation further includesproviding a forward communication link including an energizer coupled toa transmission cable, routing the transmission cable through thepredefined area in proximity to the plurality of radio frequencysensors, selectively slotting the transmission cable in regionsproximate the plurality of radio frequency sensors, transmitting radiofrequency signals through the transmission cable, and air linking radiofrequency signals to the plurality of radio frequency sensors throughthe slotted regions proximate the plurality of sensors.

A method for wireless sensor interrogation within a vehicle includesproviding a plurality of radio frequency sensors distributed within thevehicle. The method for wireless sensor interrogation further includesproviding a forward communication link including an energizer coupled toa leaky waveguide antenna, routing the leaky waveguide antenna throughthe predefined area in proximity to the plurality of radio frequencysensors, transmitting radio frequency signals through the leakywaveguide antenna, and linking radio frequency signals to the pluralityof radio frequency sensors through the leaky waveguide antenna proximatethe plurality of sensors.

These and other aspects of the invention will become apparent to thoseskilled in the art upon reading and understanding the following detaileddescription and drawings of certain exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a vehicular application of a wireless sensing systememploying separate wireless energizers and readers in the forward andreverse communication links in accordance with the present invention;

FIG. 2 illustrates a vehicular application of a wireless sensing systememploying transmission cables in the forward communication link inaccordance with the present invention;

FIG. 3 illustrates a vehicular application of a wireless sensing systememploying transmission cables in the communication links including nearfield coupling in accordance with the present invention;

FIG. 4 illustrates a vehicular application of a wireless sensing systememploying transmission cables in the communication links includingterminated coupling in accordance with the present invention;

FIG. 5 illustrates a vehicular application of a wireless sensing systememploying conventional vehicle wiring conductors in the communicationlinks including near field coupling in accordance with the presentinvention;

FIG. 6 illustrates a vehicular application of a wireless sensing systememploying pre-existing vehicle access and operation control antennas inthe sensing communication links in accordance with the presentinvention; and

FIG. 7 illustrates a vehicular application of a wireless sensing systememploying pre-existing tire pressure monitoring antennas in the sensingcommunication links in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A first embodiment of a wireless sensor system in accordance with thepresent invention is exemplified in a vehicular application illustratedwith respect to FIG. 1. Other non-automotive environments andapplications are fully within the scope of the present invention and thepresent automotive embodiment is to be understood to be offered by wayof non-limiting example of the invention. A vehicle 10 includes a numberof complex and diverse systems including sensors 11 for a variety ofmetrics related to various aspects of vehicle operation, including thenon-limiting and non-exhaustive examples of engine controls, vehicleemissions and compliance, vehicle stability including suspension,steering and wheel braking/torque controls, vehicle and occupantsecurity and occupant detection. Sensing includes non-limiting andnon-exhaustive examples of sensing environmental metrics such astemperature, humidity, pressure, light and moisture, and component,system and vehicle level metrics related to linear and rotary positions,velocities and accelerations, etc. Sensors include, for example,transducers and switches and, in accordance with the present invention,some degree of smart sensing functionality at least to enabletransformation of the sensed metrics into a form useful for wirelesscommunication. For example, some signal processing in-situ (e.g. signalconditioning and filtering, analog-to-digital (A/D) conversion) isprovided by the exemplary sensors. Additionally, sensors may be equippedwith historical data buffering and associated time stamps. And, sensorsare capable of wirelessly communicating the sensed and conditioned data,switch state or other state data when interrogated or at other times orin accordance with events as appropriate. Therefore, one skilled in theart will recognize that in addition to sensor and switch hardware,sensors 11 also include a radio frequency transponder. Such radiofrequency functionality is generally well understood and itsimplementation with sensors within the capabilities of one havingordinary skill in the art. Such sensors 11 may be further referred toherein as RF sensors.

One or more energizers (E) 13 are distributed strategically around thevehicle 10 and are effective to adequately energize the plurality of RFsensors 11 in accordance with their respective requirements (e.g. foreffecting backscatter, device powering/charging and intelligibleinterrogation). Similarly, one or more readers (R) 15 are distributedstrategically around the vehicle 10 and are effective to receive andprocess the variety of RF sensor data communicated wirelessly by theplurality of RF sensors 11 via air links 12. It is believed that, as ageneral system design premise, fewer readers (R) 15 than energizers (E)13 would be required since the forward communication links are the morelimited communication link as between the forward and reversecommunication links due to the availability of highly sensitive andselective RF front-ends and digital signal processing. A number ofconventionally combined energizer/readers (hereafter referred to hereinas transceivers (E/R)) at least as great as the number of energizers (E)13 in the present embodiment of the invention would be required toeffect the same robust coverage of the present exemplary embodiment.Advantageously, however, the physical and functional separation of theenergizers and readers in accordance with the present invention allowsfor fewer readers (R) 15 than energizers (E) 13 due to the generalimbalance between the forward and reverse communication links whichworks to the benefit of readers. Also, physical and functionalseparation of the energizers and readers in accordance with the presentinvention enables better energy utilization of both the readers and theenergizers in as much as the radiation patterns of each may be designedindependent of the other. For example, a substantially single-lobedradiation pattern 17 of an energizer (E) 13A located at a vehicle corneris preferably designed to provide forward communication link coveragewithin the general confines of the vehicle 10 with significantlyattenuated forward communication link radiation external to the vehicleas shown in FIG. 1. A substantially single-lobed radiation pattern 17 ofan energizer located at a vehicle corner is preferably designed toprovide forward communication link coverage within the general confinesof the vehicle 10 with significantly attenuated forward communicationlink radiation external to the vehicle as shown in FIG. 1. And, a morecentrally located energizer (E) 13B may be designed to provide either amore omni-directional radiation pattern 19A or, alternatively, adual-lobed radiation pattern 19B for axial coverage substantiallyaligned longitudinally with respect to the vehicle center-line, both asshown in FIG. 1. With respect to a reader in accordance with the presentinvention, similar preferential radiation patterns advantageously may bedesigned such as, for example, a symmetrical dual-lobed pattern allowingfor strategically locating the readers for effective coverage of the RFsensor transmissions in the reverse communication link.

With reference now to FIG. 2, an alternate embodiment of a wirelesssensor system in accordance with the present invention is illustratedagain with respect to an exemplary vehicular application. In thisembodiment, one or more readers (R) 15 are distributed strategicallyaround the vehicle 10 and are effective to receive and process thevariety of RF sensor data communicated wirelessly by the plurality of RFsensors 11 via air links 12. One or more transmission cables 21 arerouted through the vehicle 10 and more particularly and preferably inproximity to regions wherein RF sensors 11 are located. The transmissioncables are traveling wave antennas configured with designed leak pathsto control radiation characteristics (e.g. locations, magnitudes,cut-off frequencies and patterns) in accordance with well understooddesign principles of traveling wave and leaky waveguide antennastructures. One implementation merely requires standard shielded coaxialcable including designed regions of shielding removal to controlradiation characteristics (e.g. locations, magnitudes, cut-offfrequencies and patterns). The transmission cables are electricallycoupled to an energizer (E) 13 effective to source the cable with RFenergy as part of the forward communication link. Preferably, thecoupling is through physical termination; however, near field couplingmay be employed. Advantageously, radiated energy can be delivered andfocused by selectively leaking the energy from the cable at strategicpoints along the cable to adequately energize the plurality of RFsensors 11 in accordance with their respective requirements (e.g. foreffecting backscatter, device powering/charging and intelligibleinterrogation). This allows for efficient utilization of the energy bycontrollably radiating energy in regions requiring such radiation and byproviding relatively lossless transmission of energy between suchregions. Therefore, as exemplified in the embodiment illustrated in FIG.2, transmission cable 21 includes fully shielded transmission runs 23and slotted sensor coupling regions on either side thereof for effectingvarious radiation patterns 25 effective to adequately energize theplurality of RF sensors 11 in accordance with their respectiverequirements (e.g. for effecting backscatter, device powering/chargingand intelligible interrogation).

With reference now to FIG. 3, an alternate embodiment of a wirelesssensor system in accordance with the present invention is illustratedagain with respect to an exemplary vehicular application. In thisembodiment, one or more transmission cables 21 are routed through thevehicle 10 and more particularly and preferably in proximity to regionswherein RF sensors 11 are located. The transmission cables are travelingwave antennas configured with designed leak paths to control radiationcharacteristics (e.g. locations, magnitudes, cut-off frequencies andpatterns). At least one transceiver (E/R) 16 is air link coupled,preferably near field coupled, to the transmission cables 21 andeffective to source the cable with RF energy as part of the forwardcommunication link. As in the embodiment illustrated with respect toFIG. 2, radiated energy is delivered and focused by selectively leakingthe energy from the cable at strategic points along the cable (i.e.sensor coupling regions) to adequately energize the plurality of RFsensors 11 in accordance with their respective requirements (e.g. foreffecting backscatter, device powering/charging and intelligibleinterrogation). Additionally, in the present exemplary embodiment, thenear field coupling of the transceiver (E/R) 16 and transmission cables21 are effective in the reverse communication link of the wirelesssensing system. In this embodiment, the RF sensors are air linked to theone or more transmission cables 21 via the sensor coupling regions andthe transmission cables 21 provide near field coupling of the RF sensorsignals to the at least one transceiver (E/R) 16. Alternatively, thereverse link of the wireless sensing system may take advantage of thesensitivity benefits of readers in general with the transmission cable21 air linking to an independent reader 15 as part of the reversecommunication link. Preferably, the air link to the reader (R) 15 insuch a configuration advantageously couples to the transmission cable 21through a leak path associated with a radiation pattern 25 that alsoeffects an air link to RF sensors 11. Alternatively, dedicated leakpaths for use in coupling the transmission cable to the reader as partof the reverse communication linked may be designed; however, such apath may not be optimal from the standpoint of the forward communicationlink efficiency since such leak path would also effectively radiateenergy in the forward communication link that would not couple to and beutilized by any RF sensors 11.

With reference now to FIG. 4, another alternate embodiment of a wirelesssensor system in accordance with the present invention is illustratedwith respect to an exemplary vehicular application. In this embodiment,one or more transmission cables 21 are routed through the vehicle 10 andmore particularly and preferably in proximity to regions wherein RFsensors 11 are located. The transmission cables are traveling waveantennas configured with designed leak paths to control radiationcharacteristics (e.g. locations, magnitudes, cut-off frequencies andpatterns). At least one transceiver (E/R) 16 is coupled via physicaltermination (i.e. electrically coupled) to the transmission cable 21 andeffective to both source the transmission cable 21 with RF energy aspart of the forward communication link and receive from the transmissioncable 21 RF energy as part of the reverse communication link. As in thepreviously described embodiments using transmission cables, radiatedenergy is delivered and focused by selectively leaking the energy fromthe cable at strategic points along the cable (i.e. sensor couplingregions) to adequately energize the plurality of RF sensors 11 inaccordance with their respective requirements (e.g. for effectingbackscatter, device powering/charging and intelligible interrogation).And, the reverse communication link of the wireless sensing systemincludes the RF sensors air linked to the one or more transmissioncables 21 via the sensor coupling regions. The reverse communicationlink is then completed through the transmission cables 21 physicallyterminated at the at least one transceiver (E/R) 16.

With reference now to FIG. 5, another alternate embodiment of a wirelesssensor system in accordance with the present invention is illustratedwith respect to an exemplary vehicular application. In this embodiment,the vehicle includes pre-existing, conventional wiring harnessesincluding individual, elongated conductors 27 for providing power andground to a variety of devices including controllers, actuators andvarious electrical loads of the vehicle. Conductors 27 are welldistributed throughout the vehicle 10 with some conductors 27 inproximity to regions wherein RF sensors 11 are located. Vehicle 10 alsoincludes one or more wiring distribution centers (D) 29, terminal blocksor equivalent electrical centers whereat multiple conductors andharnesses are consolidated. In accordance with the present embodiment ofthe invention, a transceiver (E/R) 16 is positioned relative to thewiring distribution center (D) 29 for effective near field coupling viaair link 12A to both source the conductors 27 with RF energy as part ofthe forward communication link and receive from the conductors 27 RFenergy as part of the reverse communication link. In the forwardcommunication link, energy is radiated from the conductors 27 and airlinked to the plurality of RF sensors 11 for adequate energization inaccordance with their respective requirements (e.g. for effectingbackscatter, device powering/charging and intelligible interrogation).And, the reverse communication link of the wireless sensing system alsoincludes the RF sensors air linked to the conductors 27 with theremaining reverse communication link accomplished through the conductors27 and back to the transceiver (E/R) 16 across the near field air linktherebetween. Alternatively, the reverse link of the wireless sensingsystem may take advantage of the sensitivity benefits of readers ingeneral by directly air linking to an independent reader as part of thereverse communication link. Furthermore, the transceiver's energizer andreader and associated functionality may be separated as previouslydescribed with respect to other embodiments herein. For example, in analternate arrangement, an energizer may be associated with onedistribution center and a reader associated with another distributioncenter provided there is adequate signal linking 12B between the twodistribution centers via proximal conductors 27. Adequate signal linkingcan result from conductors associated with each distribution centerhaving common or sufficiently proximal routing through the vehicle, forexample. Other alternate arrangements may include various combinationsof energizers and readers near field linking to various individualconductors 27 remote from distribution centers. Since the reversecommunication link is generally subject to fewer constraints due to therobustness of the readers, such arrangement may be more preferable withrespect to reader placement than with respect to energizer placement.

With reference now to FIG. 6, a vehicle 10 includes a radio frequencyaccess control system having at least one and preferably a plurality ofdistributed antennas (i.e. antenna array) for effecting interrogation ofradio frequency access permission devices for managing vehicle security,operation and accessories. The antennas 31 are strategically located toprovide substantially complete peripheral interrogation coverage of theexternal regions of the vehicle whereat an authorized user may requireaccess, including all doors, deck lids, lift gates or other externallyoperable passenger, cargo, service, fueling or the like access points.The antenna array is coupled to at least one radio frequency transceiver(not separately illustrated). Such a system provides a radio frequencyinterrogation signal upon some externally provided request or event(hereafter an interrogation request). Such interrogation requests may beinvoked by a door handle or lift gate handle operation, an externaltouchpad switch activation or capacitive touchpad activation, or a radiofrequency signal request such as from a user activated radio frequencytransmitting key fob. Such interrogation requests are not aloneeffective to actuate access point lock hardware, but rather provide awake-up or request signal for an interrogation event from an on-vehicleaccess control system controller (not separately shown) interfacing withthe transceiver. The on-vehicle access control system remains dormantuntil such an interrogation request occurrence, whereafter the systeminvokes an interrogation signal via the transceiver at the distributedantennas 31. The interrogation is a radio frequency signal providing RFenergy and/or data signals to an RF access permission device. Thetransceiver then looks for a response back from an RF access permissiondevice carried on the individual having requested such interrogation viathe interrogation request. Such an RF access permission device may beintegrated, for example, into a key, a key fob, access card orsubstantially any object desired. In order to grant access and actuatelock hardware release, the in-vehicle access control system must receiveback from the RF access permission device information meeting thesecurity requirements for access, typically an appropriateidentification code stored within a memory structure associated with theRF device. Additionally, the antennas 31 provide substantially completeinterior interrogation coverage of the passenger compartment. The accesscontrol system can then additionally enable operative functionality ofthe vehicle systems, including keyless push-button starting andaccessory operation, in similar fashion. In such a system, theinterrogation requests may be invoked by pushing a button, flipping aswitch, turning a knob, touch pad entry or similar operator interfacewith the vehicle (e.g. pushing an engine start button, toggling a powerwindow switch, etc.). Here, again, such interrogation requests are notalone effective to start the engine or actuate the desired accessoryfunction, but rather provide a wake-up or request signal for aninterrogation event from an on-vehicle engine controller or accessorycontrol system controller interfacing with the transceiver. Thesecontrol systems remain dormant until such an interrogation requestoccurrence, whereafter the system invokes an interrogation signal viathe transceiver at the distributed antennas 31. The interrogationincludes a radio frequency signal providing RF energy and/or datasignals to the RF access permission device and subsequent response backfrom the RF access permission device carried on the individual havingrequested such interrogation via the interrogation request. As usedherein, vehicle access control includes such exemplary and non-limitingexamples of vehicle security, engine operation and accessoryfunctionality.

In accordance with the present invention, such pre-existing accesscontrol system radio frequency interrogation antenna array is alsoutilized for interrogating the plurality of RF sensors 11 within thevehicle 10 and not associated with access control functions, includingproviding RF energy and/or data signals thereto in the forwardcommunication link, and for receiving reverse communication link databack from the RF sensors 11. In the case of the RF sensors 11, however,there is no dependency upon an interrogation request invoked by thevehicle operator. Instead, interrogation of the sensors 11 occurs inresponse to system invoked interrogation requests. In other words, anon-vehicle system controller may require updated sensor data fromsensors 11 and invokes an interrogation request. The system invokes aninterrogation signal via the transceiver at the distributed antennas 31.The interrogation includes a radio frequency signal providing RF energyand/or data signals to the RF sensors 11 and subsequent responses backfrom the RF sensors 11. Radio frequency traffic from a multiplicity ofsensors 11 may be managed to avoid collisions, for example, by varioussynchronous and asynchronous techniques. Sensors 11 may, for example, bepreconfigured with predefined time slots within which they uniquelytransmit or be preconfigured with unique identifier codes whereby sensordata transmissions are managed in accordance with these identificationcodes (e.g. singulation or tree walking techniques).

With reference now to FIG. 7, a vehicle 10 includes a radio frequencytire monitor system having a plurality of antennas 33 distributed inproximity to and associated with each vehicle corner for effectinginterrogation of radio frequency tire monitor (TM) devices associatedwith each respective vehicle tire. Such antenna locations are adaptableto provide substantial vehicle interrogation coverage of the fore andaft regions of the vehicle, including engine compartments, powertrainsystems, fuel systems and suspension/chassis systems, whereatsignificant sensing operations are carried out. The TM antenna array iscoupled to at least one radio frequency transceiver not separatelyillustrated. Such a system uses the TM antenna array to receiveinformation (e.g. tire pressure or temperature or other parameters) fromthe RF TM device embedded or associated with the tire, wheel and/or tirevalue stem. Such a RF TM devices are generally operative to transmit ina self-invoked fashion. That is to say, each RF TM device will transmitbased on predefined events that are determined by the RF TM devices.These predefined events may include, for example, wheel speed (e.g. assensed by a centrifugal switch) or low/high tire pressure (as sensed bypressure switches or pressure transducers). Alternatively, suchpredefined events may wirelessly transmit an interrogation request whichtriggers the interrogation of the RF TM devices in a fashion analogousto the radio frequency signal request from a user activated radiofrequency transmitting key fob in an access control system as describedherein above. The system may further operate to avoid collisions amongthe various RF TM devices through various synchronous and asynchronoustechniques.

In accordance with the present invention, such pre-existing radiofrequency TM antenna array is also utilized for interrogating theplurality of RF sensors 11 within the vehicle 10 and not associated withtire monitoring functions, including providing RF energy and/or datasignals thereto in the forward communication link, and for receivingreverse communication link data back from the RF sensors 11. In the caseof the RF sensors 11, however, system invoked interrogations areemployed. In other words, an on-vehicle system controller may requireupdated sensor data from sensors 11 and invokes an interrogationrequest. The system invokes an interrogation signal via the transceiverat the distributed antennas 31. The interrogation includes a radiofrequency signal providing RF energy and/or data signals to the RFsensors 11 and subsequent responses back from the RF sensors 11. Here,as in the other examples where multiple RF sensors or devices aretransmitting, data collision is avoided, for example, by varioussynchronous and asynchronous techniques.

For the embodiments shown in both FIGS. 6 and 7, a communicationmechanism is required to manage the transmission of the differentsubsystems to ensure that the respective systems do not interfere witheach others' operations. Several methods could be deployed to accomplishthis, including using synchronous communication techniques andrestricting various components of the different subsystems to allottedtime intervals for the purposes of communicating. The time slots couldfurther be dynamically assigned based on vehicle state. For example,many sensors and switches do not have to communicate during periods whenthe vehicle ignition is in the off state. The communication time slotscould be devote to the other subsystem(s) for the purposes of increasingdetection probability. Asynchronous communication techniques could alsobe used including, for example, frequency and code spreading methods.With asynchronous techniques the various systems would manage thecommunication channel by spreading their information in frequency orcode in order to avoid interfering with other subsystems.

The invention has been described with specific reference to thepreferred embodiments and modifications thereto. Further modificationsand alterations may occur to others upon reading and understanding thespecification. It is intended to include all such modifications andalterations insofar as they come within the scope of the invention.

1. Wireless sensing system comprising: a plurality of radio frequencysensors distributed within a predefined area; and a forwardcommunication link including an energizer coupled to a transmissioncable, the energizer adapted to provide radio frequency signals intendedfor the plurality of radio frequency sensors to the transmission cable,the transmission cable adapted as a leaky waveguide antenna selectivelyslotted and routed within the predefined area for effective air linkingof leaked radio frequency signals to the plurality of wireless sensors.2. The wireless sensing system as claimed in claim 1 wherein theenergizer is electrically coupled to the transmission cable
 3. Thewireless sensing system as claimed in claim 1 wherein the energizer isair link coupled to the transmission cable.
 4. The wireless sensingsystem as claimed in claim 3 wherein the air link is near field.
 5. Thewireless sensing system as claimed in claim 1 further comprising areverse communication link including a reader adapted to receive radiofrequency signals from the plurality of sensors.
 6. The wireless sensingsystem as claimed in claim 5 wherein the reader is adapted to receiveradio frequency signals from the plurality of sensors exclusively viaair links.
 7. The wireless sensing system as claimed in claim 5 whereinthe reader is coupled to the transmission cable, the reader adapted toreceive radio frequency signals from the plurality of radio frequencysensors via the selectively slotted and routed leaky waveguide antennathat is the transmission cable.
 8. The wireless sensing system asclaimed in claim 7 wherein the reader is electrically coupled to thetransmission cable.
 9. The wireless sensing system as claimed in claim 7wherein the reader is air link coupled to the transmission cable. 10.The wireless sensing system as claimed in claim 8 wherein the energizeris electrically coupled to the transmission cable.
 11. The wirelesssensing system as claimed in claim 9 wherein the energizer is air linkcoupled to the transmission cable.
 12. The wireless sensing system asclaimed in claim 11 wherein the air links are near field.
 13. Thewireless sensing system as claimed in claim 10 wherein the energizer andreader comprise a transceiver.
 14. The wireless sensing system asclaimed in claim 11 wherein the energizer and reader comprise atransceiver.
 15. The wireless sensing system as claimed in claim 14wherein the air link is near field.
 16. Method for wireless sensorinterrogation, comprising: providing a plurality of radio frequencysensors distributed within a predefined area; providing a forwardcommunication link including an energizer coupled to a transmissioncable; routing the transmission cable through the predefined area inproximity to said plurality of radio frequency sensors; selectivelyslotting the transmission cable in regions proximate said plurality ofradio frequency sensors; transmitting radio frequency signals throughthe transmission cable; and air linking radio frequency signals to theplurality of radio frequency sensors through the slotted regionsproximate the plurality of sensors.
 17. Method for wireless sensorinterrogation within a vehicle, comprising: providing a plurality ofradio frequency sensors distributed within the vehicle; providing aforward communication link including an energizer coupled to a leakywaveguide antenna; routing the leaky waveguide antenna through thepredefined area in proximity to said plurality of radio frequencysensors; transmitting radio frequency signals through the leakywaveguide antenna; and air linking radio frequency signals to theplurality of radio frequency sensors through the leaky waveguide antennaproximate the plurality of sensors.